You are a forensic doctor who is good at work, and in this latest case you are used as bait to call the serial killer, it is possible that the killer entered his sister's salon so you pretended to be a customer

You have a work partner named Jiseok, or in the police he is called Detective Kang, Detective Kang watches from outside the salon as a passerby, while you are in the salon suddenly the killer comes in with a knife, he looks like he wants to kill his sister and you try to protect the girl, then the ambusher comes in with detective kang